The ability to modify the physical and chemical properties of surfaces and interfaces is important in fundamental and applied materials science. One of simplest and most common methods is to react trialkoxy- or trichlorosilanes with hydroxylated surfaces, such as metal oxides. Silanes form strong covalent oxane bonds to such surfaces, making them particularly useful for bridging the inorganic and organic components. For these reasons, silane compounds are used to prepare many important materials and devices, including catalyst-coated magnetic and mesoporous metal oxides (see, e.g., Shylesh, S., et al. Angew. Chem., Int. Ed. Engl. 2010, 49, 3428-3459), superhydrophobic surfaces (see, e.g., Crick, C. R., et al. Chem.-Eur. J. 2010, 16, 3568-3588), organic photovoltaics (see, e.g. Valentini, L., et al. Carbon 2010, 48, 861-867), thin-film transistors (see, e.g., LeMieux, M. C., et al., Science 2008, 321, 101-104), and sensors (see, e.g., Melde, B. J., et al. Sensors 2008, 8, 5202-5228) to name a few.
Conventional reactions commonly used to produce mono-, di-, and trialkoxysilanes include hydrosilylation of alkenes and alkynes, nucleophilic substitution reactions, and reactions of amines and alcohols with isocyanate-containing trialkoxysilanes. Conventional hydrosilylation of alkenes and alkynes utilizes triethoxy-, trimethoxy-, or methyldimethoxysilane and a platinum catalyst, with or without ligands (see, e.g., Alonso, J. M., et al. Langmuir 2008, 24, 448-457; Kim, Y. J., et al. Langmuir 2010, 26, 7555-7560; Sabourault, N., et al. Org. Lett. 2002, 4, 2117-2119; Uccello-Barretta, G., et al. J. Organomet. Chem. 2008, 693, 1276-1282). Nucleophilic substitution reactions rely on a nucleophilic attack of ligands on 3-halopropyltrimethoxy- or triethoxysilanes (see, e.g., Abu-Reziq, R., et al. Adv. Synth. Catal. 2007, 349, 2145-2150; Dalaigh, C. O., et al. Org. Biomol. Chem. 2006, 4, 2785-2793; Guo, Z. M., et al. Chem. Commun. 2006, 4512-4514). Reactions of amines and alcohols with isocyanate-containing trialkoxysilanes rely on reactions of amines and alcohols with 3-isocyanatopropyltrimethoxy- or triethoxysilane (see, e.g., Cui, Y. J., et al. Dyes Pigments 2008, 77, 217-222; Shiels, R. A., et al. Adv. Synth. Catal. 2008, 350, 2823-2834; Wu, Y. P., et al. Nanoscale Res. Lett. 2009, 4, 738-747). Other reactions have relied on reductive amination between 3-aminoproyltriethoxysilane and a ketone, using sodium borohydride as the reducing agent or thermal or photoinitiated radical thiol-ene chemistry to make a small amount of a single silane with either an alkene modified N,N-dimethylpyridine or terpyridine pendant functional group (see, e.g., Rissing, C., et al. Organometallics 2009, 28, 3167-3172; Killops, K. L., et al. J. Am. Chem. Soc. 2008, 130, 5062). Of the various methods used to form trialkoxysilane compounds that are known in the art, hydrosilylation is the most widely used because of typically good product yields, a ready availability of the metal catalysts, and a low cost of the trialkoxysilane precursors.
Unfortunately, all conventional methodologies for synthesizing trialkoxysilanes have significant drawbacks and limitations. For example, even though hydrosilylation reactions (e.g., hydrosilylation of alkenes and alkynes with triethoxy-, trimethoxy-, or methyldimethoxysilane) can provide good product yields, they typically require expensive metal catalysts (e.g., palladium catalysts) and/or chiral organic ligands. Hydrosilylation reactions are problematical due to their limited functional group tolerance (e.g., such reactions are not tolerant of ally esters, amides, and metal chelating functional groups), the fact that such reactions are limited to specific reaction conditions that depend on the palladium catalyst used, and further are not completely regioselective. In addition, hydrosilylation reactions can require the use of excess reagents and further require post-synthetic purification to remove metals, contaminants, and excess reactants from the moisture-sensitive products. Other conventional methodologies for synthesizing trialkoxysilanes including nucleophilic attack of ligands on 3-halopropyltrimethoxy- or triethoxysilanes, reactions of amines and alcohols with 3-isocyanatopropyltrimethoxy- or triethoxysilane, and reductive amination between 3-aminoproyltriethoxysilane and with ketones, have even more limited functional group tolerance, and are therefore limited in substrate scope, and have relatively poor product yields. Moreover, with the exception of a single hydrosilylation methodology using PtO2, which has been demonstrated to work on a large scale (see, e.g., Sabourault, N., et al. Org Lett 2002, 4, 2117-2119), all of the current methodologies listed above have only been shown to produce silanes on an approximately 1-10 mmol scale. In addition, these methodologies are also often non-quantitative, which necessitate tedious purification of the moisture sensitive compounds. As a result, although many simple and complex trialkoxysilanes can be made by conventional methods and are currently available on the commercial and retail market, a large number of them are very expensive due to their problematical synthesis regimes.
There is a need in the art for simple and inexpensive methods for producing a wide variety of desirable trialkoxysilane compounds in a relatively pure form. Additionally, there is a need for a simple way to make tailored silanes, in order to, for example, design and produce materials and devices having properties specifically selected for a wide variety of applications or that are amenable to further chemical modifications. At the same time, such processes should be environmentally friendly and not require the use of large amount of hazardous materials (e.g., solvents etc.). The invention disclosed herein addresses such needs while overcoming many of the drawbacks and disadvantages of conventional methodologies.